To read an MRI image, CT image, x-ray image, or the like in a hospital, for example, a system in which multiple displays (monitors) are connected to one computer or a display system in which one or more displays are connected to each of multiple computers which are connected through a network is often installed in a reading room. In such a system, all displays are required to display images at the same luminance and same color temperature and therefore are typically of the same model.
It is commonly known that the continued use of a display causes changes in the color temperature and luminance. Such temporal changes vary from display to display (there are individual differences). The changes in color temperature and luminance due to the continued use may vary even among the same model of displays. To correct the temporal changes in all displays in the same system so that all the displays show images at the same luminance and same color temperature, the displays are subjected to tone correction called color calibration. In color calibration, the color temperature and maximum luminance of each display are adjusted to a recommended color temperature 7500 K and a recommended maximum luminance 400 cd/m2, respectively, which are commonly believed to be appropriate for display.
There have been proposed various methods for performing color calibration among displays (for example, Patent Literatures 1 to 5).